Nitrogen Oxides Emissions Estimation for a hydrogen-fuelled Dual-Mode Ramjet in the conceptual design phase

This paper aims to investigate the P3-T3 method originally developed for nitrogen oxide emissions estimation of subsonic kerosene-fuelled aircraft and to extend its applicability to an unconventional high-speed propulsive system and to hydrogen fuelling. For this purpose, the introduction of two new variables, namely the Mach number and the Damköhler number, proves to extend the applicability of the analytical formulation up to Mach 8. The new formulation is developed thanks to the availability of 1D chemical-kinetic simulations of the combustor of the Dual-Mode Ramjet engine installed onboard the STRATOFLY MR3 vehicle, a hypersonic civil transportation vehicle with a waverider configuration. Moreover, in an effort to verify the independence of the novel P3-T3 formulation from the reference emissive database, the DLR-Stöppler formulation was considered. The upgrade of the P3-T3 method allows the mean estimation error to be reduced from 17.28%, resulting from the original formulation, to 0.399% of the novel formulation. The updated DLR-Stöppler method provided nitrogen oxide emissions assessments with a mean error of 0.405%, comparable with those of the novel P3-T3 method.